Colorant dispensers are used in paint shops and hardware stores for the custom blending of paints. Commonly, a colorant dispenser has anywhere from 9 to 18 or more canisters, each of which contains a different colorant, and a custom paint color is prepared by discharging a precisely measured quantity of colorant from one or more of the canisters into a can which contains a predetermined quantity of base white paint. This requires the use of extremely accurate metering means to discharge the requisite precise quantities of colorant from the canisters.
If a relatively small quantity of paint is to be custom blended, it is commonly done by blending specified quantities of colorant with one gallon of white paint; while larger quantities are customarily prepared by blending precise quantities of colorant with five gallons of white paint. In order to provide precise metering of the small quantities of colorant that are sometimes required, it has previously been known to provide two metering piston pumps for each canister, one pump having a maximum capacity of 1 ounce, and the other pump having a maximum capacity of 5 ounces, and there being a calibrated scale associated with each pump which permits as little as 1/96 ounce to be precisely discharged by the 1 ounce pump and as little as 5/96 of an ounce by the 5 ounce capacity pump.
Heretofore a colorant dispenser provided with two pumps also had a separate exit port for the colorant to be discharged from each of the two pumps, although a single valve controlled the flow of colorant from the canister to both pumps and from each pump to its related port.